US Patent 9989446 Sample preservation method and sample application substrate

The invention discloses a sample preservation method which comprises the following steps: a) providing a paper substrate comprising ligands, where the ligands comprise charged groups, b) applying a sample comprising at least one analyte and at least one contaminant on the paper substrate, c) drying the sample on the paper substrate and, d) extracting at least part of the paper substrate to provide a solution of the analyte.